The Consistent Behaviors of Atlantic Cod Morhpotypes within the Gulf of Maine

Diversity within populations not recognized or represented in management may lead to reductions in productivity and to population collapse. Within Atlantic cod Gadus morhua populations, physically distinct morphotypes coexist in close proximity, but their importance to population structure remains unclear. We conducted 2 acoustic telemetry studies focusing on diversity in the form of red and olive cod. Two separate arrays were established at a nearshore region of banks and ledges immediately adjacent to a major cod spawning ground and a shallow submarine seamount located 70km from shore. At each site, cod caught within the arrays were classified by color (RGR) and shape (box-truss) as red or olive, implanted with transmitters, and monitored continuously for 5 months. We predicted that red cod at both sites would remain resident in shallow areas, while olive cod would be less discriminating in their habitat choices and far more mobile; we also predicted that red cod would not participate in the active spawning occurring in deeper waters immediately adjacent to their preferred habitats. Previously observed differences in the spatial behaviors and habitat preferences of red and olive cod are ubiquitous, which may have consequences for management of cod throughout the Gulf of Maine and beyond.